# Features

Please read the code comments in the files below. Examples are taken from our [Example Contract ](https://github.com/Trac-Systems/trac-contract-example/)Github repo.

```javascript
// import the Feature superclass from the trac-peer package
import {Feature} from 'trac-peer';

export class Timer extends Feature {

    /**
    * Setup your Feature
    *
    * Instances of Features are passed to Peer instances.
    * See the Deployment section for more details.
    */
    constructor(peer, options = {}) {
        super(peer, options);
        this.update_interval = options.update_interval !== undefined &&
                                false === isNaN(parseInt(options.update_interval)) &&
                                parseInt(options.update_interval) > 0 ? parseInt(options.update_interval) : 60_000;
    }

    /**
    * start() is supposed to trigger the actual Feature execution.
    *
    * In the case of timers, an infinite event loop reads the latest
    * time every 10th second and appends it into the contract.
    *
    + The contract will then read this value as showcased in the previous
    * section.
    *
    * Appends from Features don't go through transactions but straight into
    * the contract.
    */
    async start(options = {}) {
        while(true){
            await this.append('currentTime', Date.now());
            await this.sleep(this.update_interval);
        }
    }

    // stop helps to shutdown and may be triggered by a custom Feature-handler
    async stop(options = {}) { }
}

export default Timer;
```